In the women's peloton, it's not uncommon to take a "pee break." Typically this will be initiated by the race leader (in a stage race). Like the men, it's uncool to attack during the break.

It's not uncommon to see this happen relatively early in the race (pace is still slower so HRs are lower, everyone's still well hydrated or had some morning coffee, etc). In the pro races, they'll actually announce this on the tour radio (the radio that goes into all the team cars and narrates the race).

At Redlands last year, when the women took their break, the caravan did too (which was good because I'd had too much coffee and was dying). It was a little weird, because all the male team directors and mechanics just stood off to the side of the road, but the few women had to find somewhere a bit more discreet to squat.